Track-type machines are used in a wide variety of rugged service environments. The use of ground engaging tracks rather than wheels can provide enhanced traction, stability, and robustness to a machine system over what might otherwise be available. A typical undercarriage system in a track-type machine includes a plurality of track shoes coupled together in an endless roller track chain by way of a set of track links, and extending about a drive sprocket and one or more rotatable idler wheels. The track assembly provides better mobility on uneven ground and typically renders excellent traction while spreading the weight of the machine over a large area. Mining, construction, landfills, forestry, and still other service environments are notable examples of where track-type machines are advantageously used.
The idler wheel at the front of the undercarriage can have an adjustable position to control the tension in the roller track. Also, the front idler wheel may be mounted on a frame of the undercarriage by a recoil assembly that allows the idler wheel to deflect rearward when impacted by an obstacle in the path of the track-type machine to prevent damage to the undercarriage. Recoil assemblies for idler wheels of undercarriages are known in the art. For example, U.S. Pat. No. 3,899,218 issued to Blomstrom et al. on Aug. 12, 1975, entitled “Combined Integral Component Enclosure and Track Roller Frame,” discloses a track roller frame with a front idler connected to a box beam of the track roller frame by a carriage between a pivot pin about which the front idler rotates and a pivot pin about which the carriage rotates. A rearward arm of the carriage is pivotally connected to a yoke assembly that in turn is connected to a rod of a recoil mechanism. This arrangement applies proper tension to the roller track and allows obstacles in the path of movement to be traversed with a minimum shock to the undercarriage.
In track-type machines such as finish grading machines, an idler rise height of the idler wheel can affect the smoothness of the ride of the machine and its ability to smoothly grade a work surface. When the idler rise height is too high, a track roller directly behind the idler wheel may do most of the work of getting grousers extending from the links or shoes of the roller track penetrated into the work surface. Moreover, the total track length in contact with the work surface is shortened, which can cause the track-type machine to lose balance and lead to poor fine grading performance. When the idler rise height is too low, the idler wheel must do all the work of getting the grousers to penetrate the work surface. Also, the roller track can have a tendency to buckle between the idler wheel and the first track roller, which can cause the track-type machine to bounce up and down each time a grouser passes under the idler wheel and again lead to poor fine grading performance. When the idler rise height is set correctly, an optimum total track length on the work surface is achieved, and the idler wheel begins penetrating the grousers into the work surface and the track roller behind the idler wheel completes the grouser penetration, which leads to optimum finish grading performance.